The present invention is directed generally to the testing and characterization of radio transmission and receiving devices. More particularly, the invention pertains to a system and method for testing and characterizing such equipment under controlled conditions of signal impairment, including path loss, interference, noise, and the like.
When building radio systems such as cordless telephones, cellular telephones, cordless modems and other transmitting and receiving equipment, there exists a class of problem generally referred to as range testing. By definition, a radio must transmit through free space to a receiving end some undetermined distance away. Range testing involves the characterization of the radio to determination of its effective operating range. This is the range or distance the radio can effectively communicate to a remote receiver. Range testing also determines the radio's associated tolerance to interference and noise.
Ideally, the range testing of one or more radios that are to communicate with one another, or with test equipment, should be performed under the controlled application of various signal impairment conditions such as path loss, interference and noise. To date, a mechanism has not existed which allows this type of control. Range testing has been conventionally performed in an outdoor environment. One radio is stationed at a first location located a meter or two above the ground. A second radio is then moved away from the first radio while periodic communication tests are performed. The distance at which the two radios stop communicating or when the noise on the audio channel, as determined by users listening to the radios as they are separated, determines the operating range or distance. This is the number that many manufacturers place on the product packaging that consumers see at retail stores.
The prior art range testing method is both arbitrary and inefficient. The conditions under which such testing occurs can be greatly influenced by the terrain surrounding the testing location and by changing environmental conditions. What is needed is a controlled environment where repeatable experiments can be run in a laboratory setting. What is especially required is the ability to controllably apply various signal impairment conditions such as path loss, interference and noise, while accurately quantifying the effect of such changes on the radio equipment being tested.